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Re: [public-houdini] <none>

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 16 Mar 2015 16:53:38 +1300
Message-ID: <CAOp6jLY5R1kPdCuTqHkLZFWBvosOp-SFbnX4BX+a=7Rt0rLoVA@mail.gmail.com>
To: Ian Vollick <vollick@chromium.org>
Cc: "public-houdini@w3.org" <public-houdini@w3.org>, Rick Byers <rbyers@chromium.org>, Dean Jackson <dino@apple.com>, Simon Fraser <simon.fraser@apple.com>
On Sat, Mar 14, 2015 at 12:17 PM, Ian Vollick <vollick@chromium.org> wrote:

> On Mon, Mar 9, 2015 at 9:02 PM Robert O'Callahan <robert@ocallahan.org>
> wrote:
>> With #2, if you think of the control thread being your primary
>> application thread, all the async APIs you could want are available, by
>> postMessaging to the main thread.
>> For #2, we can provide most existing APIs to a control thread Worker ---
>> except DOM manipulation (and by extension, full manipulation of CSS
>> layout). For example, if we want to animate CSS 'width' at 60fps with text
>> wrapping and border redrawing, we need #1. To some extent, #2 leads
>> developers away from using CSS and the DOM. It seems very unappealing to
>> replicate features like editable content, accessibility, text input and
>> rich text layout outside of CSS and the DOM, so if we end up wanting these
>> on the control thread, that's a problem for #2.
> This is a fair concern, but I don’t think we’d have to reimplement all
> these features. As I understand it, approach #2 would still permit an
> application to be constructed in terms of components built out of DOM/CSS
> with accessibility, input etc. And as you mentioned earlier, we’ll have
> access to all of these from the control thread, though asynchronously.

Right. The question is how much demand there would be for those features to
be accessibly synchronously to a non-main-thread control thread.

A critical question is whether #2 leads to a coherent application
>> development approach which integrates 60fps application rendering with
>> chunks of not-60fps CSS-rendered content, or whether it leads to an
>> architecture which is not compelling to developers, or whether it leads to
>> a bifurcation in the Web where apps and documents use separate APIs (and
>> how bad would that be?).
>> Personally I lean towards #2 currently, but I don't know enough to
>> predict the implications.
> Fantastic questions. I don’t think that #2 precludes components, even if
> they disagree about the choice of control thread, provided we’re willing to
> stomach some asynchrony in their interactions.
> About the bifurcation -- there will certainly be an asymmetry in
> programming paradigms, but that might actually be a benefit. In an
> application where some code is performance-critical and some isn’t, the way
> you write the fast stuff is often very different (eg, shaders). This is
> handy both because it reminds you that you’re writing performance-critical
> code and because the manner in which you’re forced to write this code can
> make it tough to cause performance problems. It’s designed to be performant
> and to minimize footguns.
> As for whether it leads to an architecture which is not compelling to
> developers, it’s really tough to say. The approach should permit
> incremental (pay-to-play) adoption of performance isolation (so if not
> compelling, hopefully not scary) and it seems like it might benefit some
> existing frameworks, but I'd really like to do some experiments, build some
> real, non-toy things, and see how it feels in practice.


I think the animation-timeline proposal is control-thread-agnostic so we
could progress that towards shipping, in parallel with other work, if
people feel it's useful enough.

Meanwhile, I think we should produce a consensus proposal for a minimum
viable Worker-control-thread API. Can you provide a link to your latest

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Received on Monday, 16 March 2015 03:54:05 UTC

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